This invention relates generally to the automotive arts and more particularly to an adjusting mechanism for an automobile headlamp assembly. Still more particularly, the invention relates to a novel and improved adjusting mechanism employing a plastic adjustment gear and a drive member retaining arrangement.
Mechanisms for vertical and horizontal adjustment or "aiming" of automobile headlamps have been provided for sealed beam-type automotive headlamps for some time. Generally speaking, such headlamps were individually adjustable with independent adjusting screws or the like, by driving the same with a suitable mating tool. often, these adjusting screws were accessible only with difficulty or upon time consuming removal of certain trim or bezel components of the headlamp assembly. Problems have been encountered in that these adjusting screws became corroded or otherwise fouled with rust and/or road grime, rendering the adjustment procedure inordinately time-consuming and difficult, or necessitating removal and replacement of a number of parts.
With the introduction of composite headlamp assemblies, and to overcome the aforementioned problems, novel types fo adjusting mechanisms have been utilized which mount interiorly of the vehicle and can be easily and readily operated to adjust vertical and/or horizontal positioning or "tilting" of the headlamps to achieve the desired aiming thereof. Such a mechanism is independent of the headlamp members or other headlamp assemblies, such that it could be used with any of a wide variety of different headlamp sizes, shapes and configurations as well as other inaccessible devices needing adjustments, interchangeably.
While the art has developed a bevel gear configuration which transposes vertically applied rotational input to create a linear horizontal adjustment and the art has refined the general configuration of the adjustment mechanism, those skilled in the art generally have been unsuccessful in implementing a plastic gear configuration. It was heretofore generally accepted that attempts at utilizing plastic gears would fail due to the high tooth load and deflection which is applied to the gears in this application, to overcome the prevailing torque that must be built into each assembly to assume the headlamp remains in position once adjusted.
However, we have found that the use of plastic for the adjustment mechanism gears is highly desirable for reasons of both economy and perfomance. Plastic is suitable especially for the output gear because the output gear will then produce or create the prevailing torque on the output adjustment member, a threaded screw member, to prevent it from moving or being moved out of adjustment. The metal gears used in the prior art adjustment mechanism arrangements usually require an additional supplementary frictional means which assist in retaining the desired adjustment achieved through utilization of the adjustment mechanism.
Presently available adjustment mechanisms utilize a drive gear in cooperation with an adjustment gear, both gears being bevel gears formed of metal. To help retain the desired adjustment once it is set, the adjustment gear is formed to receive a plastic bushing inserted through the center. It is the threading of the adjustment member into this plastic bushing which provides the prevailing torque on the output member screw to prevent the mechanism from changing its adjustment due to mechanical vibration or impact. In this regard the plastic brushing is initially unthreaded, and the engagement of the threaded output member therewith deforms the plastic material to provide a mating female thread. As can be appreciated this thread forming operation produces high frictional flank-to-flank engagement, that achieves the desired prevailing torque.
The problem with the use of a plastic bushing inside the metal adjustment gear is that is creates additional parts to be manufactured, monitored, warehoused and assembled and provides another component of the overall assembly which could be flawed or fail thereby reducing the reliability of the overall assembly.
It was heretofore believed impossible to utilize plastic gears in this arrangement because the teeth of the plastic gears failed under the applied torque, such that the teeth deflected or were sheared off due to the extreme load. Further, it was also though that the molding problem one would encounter with a plastic gear would render such a gear type uneconomical. However, the present invention has now solved the problems of using plastic gears in such an adjustment mechanism.
As an additional matter, this type of adjustment mechanism requires an adjustment drive member to be positively maintained attached to the drive gear which is retained within the gear housing. Prior art mechanisms have retained this drive member in place by adhesively attaching one end of the drive member into a recepatacle formed in the surface of the drive gear. While the adhesive was theoretically capable of retaining the drive member many problems were created. First, too much adhesive resulted in the adhesive overflowig the drive member receptacle and flowing between the drive gear teeth and the adjustment gear teeth or into other parts of the assembly thereby interfering with the operation thereof. Second, too little adhesive resulted in the shaft coming loose from the shaft retaining receptacle thereby requiring reaffixing or replacing the drive member.
The present invention, as will be detailed more fully hereinafter, overcomes the above-described problems. More specifically, the present invention provides a novel and improved headlamp adjustment mechanism utilizing a plastic gear arrangement which also non-adhesively retains an adjustment drive member.